Engine and trans fitment questions for my 64 Beetle

[mlew]

I did not really want to grind and clearance my trans since I need to change it. Could still be a option. I have a lead on a 67 swing axle and I do believe they are 12v. Hopefully it will bolt in and work.

[drs1023]

Type 1 engines are interchangeable on type 1 transmissions as far as bolt pattern, clutch arm alignment, etc. The flywheel is not as simple but do-able in a coupla' hours. The 12 V flywheel (200 MM), will not fit into a '65 and back transmission without grinding off some clearance points (shiny areas) as is shown here the last time I did it. The 6 V starter will engage the flywheel and will last a long time with 12 V power. If you want to change the starter to 12 V, you must change out the bushing for the starter to one compatible with the 12 V. Or - you can install the 12 V auto-stick starter which requires no bushing. That's what I've done on a few occasions as shown here.

I don't know how direct the interchange is between swing axle and IRS transmissions. Lot's of folks here know that off the top of their head.

[mlew]

I am looking to replace the engine in my 64 Beetle and wanted a little more power that the stock 40hp that’s in it now. I have my eye on a 1600 dual port that is ready to install. Will it be a direct fit or is there any modifications that will need to be done?
The car is currently 6V and I want to convert to 12v since the new DP engine has a 12V generator. Changing the lights and other things is straight forward but I am confused about the differences in the 6V and 12V flywheels. I wanted to replace the transmission at the same time because it leaks more oil than the engine does it is hard to shift even though I have replaced all the shift bushings. I am a little confused on which way to go.

What year transmission do I need to match to the 12V flywheel on the new engine that will bolt into my 64? I am thinking that any 12V swing axle trans will bolt in, am I right?